Update index.md

Add the OSL file

Author: woshimajintao

docs/index.md

@@ -31,6 +31,8 @@ This tool helps you annotate action spotting datasets in sports video. Use the n
 - [Installation](installation.md)
 - [User Guide](gui_overview.md)
 - [FAQ](faq.md)
+- [OSL JSON format](OSL.md)
+
 
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